1. Field of the Invention
This invention relates to a method for cleaning and disinfecting contact lenses and a composition for the same. More specifically, the present invention is directed to a method for simultaneously cleaning and disinfecting contact lenses by contacting the lenses with an aqueous system containing an antimicrobial agent and a proteolytic enzyme. A composition for simultaneously cleaning and disinfecting the lenses is also provided.
2. Description of Art
In the normal course of wearing contact lenses, tear film and debris consisting of proteinaceous, oily, sebaceous, and related organic matter have a tendency to deposit and build up on lens surfaces. As part of the routine care regimen, contact lenses must be cleaned to remove these tear film deposits and debris. If these deposits are not properly removed, both the wettability and optical clarity of the lenses is substantially reduced causing discomfort for the wearer.
Further, contact lenses, especially those made from hydrophilic materials, must be continuously disinfected to kill any harmful microorganisms that may be present or grow on the lenses. A number of methods for disinfecting contact lenses have been used such as the use of high temperatures, the use of oxidative chemicals, and the use of antimicrobial agents. However, current disinfecting solutions do not exhibit significant cleaning ability for the removal of proteinaceous material.
Conventionally, the cleaning of contact lenses is accomplished with one or both of two general classes of cleaners. Surfactant cleaners, generally known as "daily cleaners" because of their recommended daily use, are effective for the removal of most carbohydrate and lipid derived matter. However, they are not as effective for the removal of proteinaceous matter such as lysozyme. Typically, proteolytic enzymes derived from plant, animal, and microbial sources are used to remove the proteinaceous deposits. These "enzyme" cleaners are recommended for weekly use and are conventionally employed by dissolving enzyme tablets in suitable aqueous solutions.
The process of cleaning and disinfecting contact lenses with enzyme cleaners (as well as daily cleaners) involves two steps. The first step consists of the cleaning phase whereby lenses are conventionally soaked in an enzyme cleaning solution at ambient temperature conditions, i.e., cold soaking for a period of up to 12 hours, to achieve effective removal of proteinaceous deposits. At the conclusion of the cleaning step, the lenses are separately disinfected. Disinfection involves contacting the lenses with a solution containing either an oxidative chemical or an antimicrobial agent at ambient temperatures or exposing the lenses to elevated temperatures for specified periods of time. The latter disinfection technique requires specific electrical disinfecting apparatus.
New methods have been developed which can remove proteinaceous material from contact lenses while disinfecting the lenses. For example, U.S. Pat. No. 4,614,549 discloses a single-step method of cleaning and disinfecting contact lenses in aqueous solutions of proteolytic enzymes at temperatures of between 60.degree. C. and 100.degree. C. This method requires the use of electrical disinfecting apparatus and elevated temperatures. U.S. Pat. No. Re. 32,672 discloses a method which immerses the lenses in a solution containing peroxide and a peroxide-active enzyme. However, this method requires an additional step for the neutralization of the residual peroxide prior to inserting the lens into the eye.
In order to develop an improved simultaneous cleaning and disinfecting method that does not require neutralization of any oxidative chemical, proteolytic enzymes in tablet form were tested in combination with a disinfecting solution containing hexamethylene biguanide polymers as the antimicrobial agent at ambient conditions. However, subsequent microbicidal efficacy studies revealed that the antimicrobial agent was rendered less effective for killing certain microorganisms during these initial studies.
However, it has now been discovered that the disinfecting ability of antimicrobial agents, particularly at ambient temperatures, is most effective under conditions of suitable osmolality for the agent employed. When the osmotic level of the solution is too high, the antimicrobial agents are rendered less effective for killing certain microorganisms.
Thus, according to this invention, proteolytic enzymes can be used in combination with antimicrobial agents to simultaneously clean and disinfect contact lenses. Under ambient temperatures, the disinfection has been found to be most effective at suitable osmotic conditions. The present invention provides a less complex and more convenient regimen for cleaning and disinfecting contact lenses without the need for a separate neutralizing step or electrical disinfecting apparatus.